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#### About Port Clearance Distances

Use the Clearance distances area in the Probe Changer Port Data dialog box to define two different clearance distances from the port that your machine can use before dropping off and picking up hardware.

Clearance distances area

You can also define clearance distances and tie them to specific probe tips. To do this:

1. From the menu, select Insert | Hardware Definition | Probe to display the Probe Utilities dialog box.

2. From the dialog box, click the Setup button to display the Probe Setup dialog box.

3. Make your changes in the Clearance distance areas and then click OK.

Any probe-specific values defined take precedence over those defined in the Clearance distance areas. For more information, see "Using Probe-Specific Port Clearance Distances".

In versions prior to PC-DMIS 2009, there was only a single clearance distance that you could specify, and you had to use the Settings Editor. Now you can define these different distances directly within PC-DMIS. These distances affect the motion during a probe change operation.

Before drop-off - Specifies the clearance distance PC-DMIS uses when the probe is still attached. This distance applies before dropping off a probe to the port, but it also applies after picking up a probe from this port.

Before pick-up - Specifies the clearance distance PC-DMIS uses when there is no probe attached.

The main reason for having these two distinct clearance values available to each port is to better accommodate probe configurations that have a stylus pointing back into the rack. In the example below, the star probe contains a stylus pointing towards the rack. Some example clearance lines are also provided on the image to illustrate the two separate clearance distances.

Example showing before pick-up (line A) and before drop-off (line B) clearance distances

In these types of probe configurations, additional clearance distance may be needed to move to the clearance location without colliding with other probes stored in the rack. For example, using the sample image above, a mount point may have been defined in a central area of the rack (such as the area in front of port 4 or 5). For a probe change that drops off the current star probe in port 1 and picks up the new one from port 2, when moving from the mount point to the clearance location for port 1, a collision could occur between the star probe's stylus that points toward the rack and the probe in port 2. In this case, a Before drop-off distance (indicated as line B) would provide the needed clearance. Yet, since that extra clearance distance is no longer needed when moving between the drop-off and pick-up ports with no probe attached, the Before pick-up distance (indicated as line A) is also beneficial.

Consider this Example

Again, using the image above, a typical probe change cycle, where the current probe is dropped off into port 1 and a new probe is picked up from port 2, could be described as follows:

1. The machine moves to the defined mount point for the probe changer.

2. The machine moves to the Before drop-off clearance location for port 1 (line B)

3. The machine moves into port 1 and drops off the current probe.

4. The machine moves back out to the Before pick-up clearance location for port 1 (line A).

5. It moves to the Before pick-up clearance location for port 2 (line A).

6. It moves into port 2 and picks up the new probe.

7. It backs out to the Before drop-off clearance location for port 2 (line B).

8. It moves back out to the defined mount point.

Affected Probe Changers

Although these clearance values can be specified for almost all tool changer types, it’s possible that they may not have any effect in some cases. For some of the machine-specific changer types, where the change cycle is handled by the particular machine interface, it’s possible that the interface has not implemented this functionality. Additionally, there may be some machine-specific changer types where the change cycle motion is handled by the machine controller itself and therefore is not under the direct control of PC-DMIS.

Initial Default Clearance Values

You can modify the initial default clearance values for specific probe changer types by modifying the appropriate registry entries in the PC-DMIS Settings Editor. These registry entries are in the Option section of the Settings Editor:

- TCDefaultClearanceBeforeDropoff_<Changer> - This is the before drop-off clearance distance in millimeters for the probe changer type referred to by <Changer>

- TCDefaultClearanceBeforePickup_<Changer> - This is the before pick-up clearance distance in millimeters for the probe changer type referred to by <Changer>

For example, a TP20 probe changer would have variable names of:

- TCDefaultClearanceBeforeDropoff_TP20

- TCDefaultClearanceBeforePickup_TP20

If these new variables have not been customized for a given changer type, PC-DMIS still looks for the possible existence of a customized value from the older clearance-related registry entry that was available for some types. If found, it applies that value to both clearances until that older variable is deleted or the new customized values are saved using the above registry entries. These older clearance-related registry entries should be considered deprecated:

- AutochangeClearance

- ACR3Clearance

- FCR25Clearance

- SCP80Clearance

- TESASTAR-PRClearance

- TESASTAR-RClearance

- TP20Clearance